DerekL1963

That's difficult in two respects - first, you'd need some truly huge balloons as hydrogen only lifts about 60lbs/1000ft^3 (.22kg/m^3) at STP. The second is that the gaseous hydrogen is going to be cold - nearly cryogenic, giving it even less lifting force. (And finding a balloon material that is a) light enough, b) strong enough to withstand deployment forces, and c) not going to crumble at near cryogenic temperatures... is going to be really, really interesting.) And how exactly are balloons that are above the booster going to act as airbags, which need to be below it?

I didn't say it won't work - I said it's theoretical. Words mean things, and "won't work" and "theoretical" aren't synonyms Nobody has ever actually detonated one of the propulsion units in space and actually determined how much push it will give. (Though it makes one king h--l of a shaped charge and if the rumors are true it's been tested on the ground.) and is the reason all but the gross details of the propulsion units are still classified.) Nobody has ever exposed a pusher plate to the resulting plasma. Nobody has ever built the shock absorption system except at the crudest scale. Etc... etc... Precisely nothing about the performance of the drive system is known with certainty. Meanwhile, the F9H is an expansion of an existing and more-or-less well proven vehicle. If you call them both equally theoretical, well... that just makes no sense.

OK, I didn't know that. Though it seems to me that either way, the effective nozzle of the afterburner section would be the exit plane of the tailpipe. Either way, rocket designers do their damnedest to ensure combustion is complete before the throat for maximum efficiency. (So sayeth a friend who designs and builds rockets for a living.)

Keep in mind that Orion is itself just barely this side of theoretical, pretty much no significant part of the propulsion system has been tested beyond the crudest of scale models.

Well, no. The working principle is entirely different in that most jet engines don't actually have a nozzle anything like a rockets. (And for those that do, it's right at the exit of the tailpipe - downstream of the afterburner.)

The specification is a hobbyist launcher - private citizens don't have access to F14's, even if it were still in service. (It isn't.) Even if they did, it's a very expensive aircraft to operate.

Not knowing your qualifications, so no offense intended; If you can write it up and post it somewhere that isn't the forums (a Google doc? a blog post?), I'd love to point some real rocket scientists that I know towards it.

If you want to significantly increase the cost, sure. Landbased pads, especially for a vehicle this size, are cheap, cheap, cheap. (Basically a square of concrete and a smallish rolling building.) Custom modified aircraft... are not.

AIUI Generally you want combustion to occur before the point of highest density and velocity (usually the throat of the engine) for maximum efficiency. While this engine does capture some energy that would otherwise be wasted, it goes out of it's way to create that wasted energy... My gut (which has nothing really backing it up to be honest) says there's something basically wrong with this scheme.

I didn't just "shout" "you can't do that". I told you multiple times that you need to know the mass before you could calculate TWR. This is now the fifth time I've said this. You start with the mass. You can start with an estimated or target TWR (what you keep calling a known TWR), but then you have to determine (or estimate) the mass and use that with the thrust of your chosen engine to calculate the actual TWR. If the latter doesn't equal or exceed the former, you iterate. You choose a new level of engine performance or you start slashing your weight. Now that we've seen your masses, we know that your estimates are likely on the low side - time to iterate. Something has to give or change. That's because it's the first time you've given the information I asked for in my very first response to you, the information I needed in order to analyze your design - before you provided the numbers I had no idea what you had or hadn't taken into account in calculating your dry mass. (And wasn't going to assume a priori that you hadn't.) In the same vein, you'll note that specific criticisms (like sevenperforce's) are in response to actually posting numbers. Squid, I gave you alternatives in every single post (see the first line of this reply), and you just kept repeating the same thing back to me. That's very frustrating and why I went close to going too far.

As is the difficulties of handling hydrogen peroxide.

At least in the US, relatively few houses have deliberate systems that circulate air in and out. That's why sick building syndrome became, and still is, an issue - modern buildings are built very tight to conserve energy and counterflow heat exchangers to combat this have really only relatively recently become a thing. Even with a 'tight' house, combustion based heating takes relatively small amounts of air relative to the volume of the house so they just rely on leakage to make up the difference. (Though there's starting to be a trend towards taking combustion air from the outside rather than using air you've spent money to heat.)

Smaller though. We can build much lighter structures, have more efficient engines, and the guidance system and electronics (which have to be carried most of the way even in an Explorer I configuration) are orders of magnitude lighter.

Small kits or HPR?

So? Since we aren't talking about a sudden growth and spread of microorganisms in a place they previously hadn't been present, this isn't relevant in any way, shape, or form. You already breathe soil microorganisms (and much worse microorganisms) 24/7/365 every single day of your life.

In the near term (several decades), all off planet colonies are going to depend on a large degree on imports. Additive manufacturing is the key to relieving much of that, but we're a long way from a 3D printer that can 'close the loop' buy printing copies of itself as well as being able to print the machinery needed to gather and process raw materials into feedstock for itself. The real cork in genie's bottle however is IC's - we can't even produce 1960's grade (SSI) without a significantly complex processing chain and fabrication plant. 1970's grade (something on the order of the Intel 4004) is even more complex and demanding. Turn-of-the-century grade? Fuhgettaboutit.

Not really. It's not the performance of the booster, it's the location of the launch site - it presumes 'canned' payloads that can withstand long storage or extensive additional infrastructure in a place where such things are expensive. Plus it gives up the key reasons they looked into ALASA in the first place, the availability of a wide range of launch azimuths and the ability to fly to a launch point where the weather isn't. (It's the wide range of azimuths that's the key, you can choose one that places a recon bird over the area of interest in the shortest possible time.) Using an offshore pad really isn't much of an option, they're somewhat at the mercy of the weather (less than a fixed base, more than an airplane) and very expensive to maintain on 24/7 alert to get underway or to maintain underway 24/7. A friend worked on ALASA... his description of some of the propellant testing used a goodly number of 'colorful Anglo-Saxon monosyllables'.

Then why haven't you shown your design despite being asked for it? Why has it been like pulling teeth to obtain those numbers? o.0 No, you can't know the TWR unless you know the mass. I cannot repeat and emphasize this enough, it's one of the most basic axioms of rocket design. (You can assume the TWR, but that's treading on very, very thin engineering ice.) The mass is the starting condition for the booster and the foundation for all other calculations. That's not an alternative method - it's the only method. That being said, those numbers look way off, two tons of aeroshell (even without TPS) isn't going to buy you much in the way of structure. (And I wouldn't be surprised if your thrust web ended up eating a significant fraction of that.) And are the control surfaces included in that? Where is your recovery system (parachutes and landing gear) in your weight estimates? For that matter, what is your recovery method? Your tank estimates seem similarly off - you can't use conventional rocket numbers as these tanks will have to take stresses in directions that a conventional rocket doesn't, meaning your tanks will be heavier as will your structure. I have tried repeatedly to offer constructive criticism, only to be shot down because you don't seem to grasp what I'm saying. Serious question, is English your native language? Because we have a communications gap, and it's either language or you really don't grasp the engineering as well as you think you do and don't (or won't) grasp the existence of the gap. (And no, this is not ad hominem. I have yet to make such an "attack", nor do I plan to. Pointing out the errors in your design process is not an attack.)

Yes, I did read the entire post - that's why I questioned the validity of your mass estimates in the first place, because you very obviously hadn't made any. You started with TWR - a number you can't possibly know because you don't know the mass. *That* is why I call your mass numbers something pulled out of thin air. Because you didn't estimate the mass of your vehicle and work the equations forwards, you worked them backwards starting with numbers that aren't valid unless you know the mass to start with. You can do that in high school algebra, in abstract problems - but you can't do it engineering, in real world problems. You haven't estimated the actual weight, you've derived the theoretical maximum weight and then presented it as the actual weight. And failed to grasp that there is a difference between the two. It's cargo cult engineering at it's finest, people know that terms are important, but they don't know what they actually mean or how they're actually arrived at.

No, I am not just rattling off words, I understand them, and clearly you did not read any of my post. I did not pull terms out of thin air, which I EXPLAINED in my post. I play KSP, I read aerospace engineering articles in my free time, and I am not just coming through and shouting "I think we need a big streamlined aerocapped superthruster" I derived all masses from TWR, engine thrust, and the fuel mass to tank mass ratio You can't "derive" any mass from TWR and engine thrust - because you can't know TWR unless you know the mass first! I very clearly did read your post and you very clearly are pulling stuff from thin air. So, I'll repeat my question - how did you arrive at your figures for dry mass?

It's something like "model years" are for cars, a way of identifying a particular configuration or performance level or whatever.

That would because you *are*, and the same with your "back of the envelope" stats. It's just number salad because you've pulled terms and numbers out of thin air. (Or, if they aren't from thin air, show your work - how did you derive dry mass?)

Sometimes we open our windows and are walking outdoors, so we are not inhaling their spores 24/7/365 and every day we decrease their concentration in air. There are little critters in the outside air too, so yes - we are inhaling them 24/7/365. And if we only "sometimes" open windows, then we are not "every day decreasing their concentration". Try again.

Isn't that really just Delta Clipper More just a collection of random buzzwords. Less of a LEGO spacecraft and more of Scrabble spacecraft.

As they say [[citation needed]]. We already live, 24/7/365, in an environment swarming with those microbes with no noticeable detrimental effects save when a house gets overwhelmed with mold growth.